NASA managers Wednesday cleared the shuttle Endeavour for a predawn launch February 7, the first of a final five space station assembly flights before the shuttle fleet is retired later this year.

The countdown is scheduled to begin at 2 a.m. EST on February 4, setting up a launch attempt at 4:39 a.m. February 7 from launch pad 39A at the Kennedy Space Center. It is the last planned night launch on the shuttle schedule.

The Tranquility module, being loaded into the shuttle Endeavour's payload bay at launch pad 39A on January 23. The new module will house life support equipment, exercise gear, and a robotics work station.
NASA

"We reviewed all aspects of the shuttle and the space station," Bill Gerstenmaier, chief of space flight operations, said after an executive-level flight readiness review. "It was an extremely thorough review. We set the launch date for February 7 at 4:39 and so far, things look pretty good."

"We're not looking at any problems," he told reporters. "We have a good, low constraints count now in the firing room, so really in great shape there."

Assuming an on-time launch, commander George Zamka, pilot Terry Virts, Kathryn Hire, flight engineer Stephen Robinson, and spacewalkers Robert Behnken and Nicholas Patrick plan to dock with the International Space Station two days later, at around 1:23 a.m. February 9.

The primary goal of the flight is to attach the new Tranquility module, or node 3, to the left side of the lab complex to house life support gear, exercise equipment and a robotics work station. Three spacewalks by Behnken and Patrick are planned before undocking February 17 and landing back at the Kennedy Space Center around 11:16 p.m. on February 19.

"We're embarking on probably the last of the assembly flights to install a complicated module on the ISS," said station Program Manager Mike Suffredini. "There are still other assembly flights ahead of us, but node 3 is probably the last of the very complicated modules that'll have its own cooling system and be the home of all the regenerative (environmental control and life support) systems as well as some other critical systems that support the crew on orbit."

The astronauts will attach Tranquility to the left port of the central Unity module. Electrical and data lines will be connected, along with hoses that will tie the new module into the station's two independent ammonia coolant loops.

NASA originally planned to attach Tranquility to Unity's Earth-facing port, but engineers decided to move it to the left side of the module to improve options for docking future commercial cargo ships and NASA's planned Orion crew transfer vehicle.

But connectors needed to circulate ammonia coolant to and from Tranquility were not correctly positioned, or "clocked," for Tranquility to be attached to Unity's left-side port. Long extension hoses were ordered, but problems during recent pressure tests forced NASA to develop an alternative approach.

NASA managers ultimately decided to connect shorter flight-qualified hoses to solve the problem while improvements were ordered to bring the longer hoses up to flight standards as a backup. Suffredini said the modified shorter hoses were ready for shipment to the Kennedy Space Center.

"All of that allows us to activate the node and begin the process of installing the (life support system) racks into node 3," he said.

But first, engineers want to get run time on a new urine processor system distillation assembly being ferried up aboard Endeavour.

The station's urine processing system, which converts urine into ultra-pure water for drinking, crew hygiene, and oxygen generation, has been shut down in recent weeks because of problems with a critical distillation assembly. More recently, blockage in a line knocked out the part of the system that converts condensate into clean water.

"We brought home the other failed distillation assembly on the last shuttle flight," Suffredini said. "Through a failure investigation, we found calcium deposits inside the distillation assembly and we're doing quite a bit of investigation to determine how to prevent that in the future.

"One way is to not process to as high a concentration of brine inside the system, meaning we empty the tank that carries the ultimate waste from the urine processor, we empty it a little more often. So we want to run the processor with the new distillation assembly inside long enough to fill the tank up to the new level we plan to operate at, remove that tank, and bring it home.

"That will take us almost the entire mission, from the time we're able to install the spare until the time the crew has to depart," Suffredini said. "That's what's driving us not to do the rest of the rack moves until the urine processor can move."

As for the presumed line blockage problem with the water processing system that is preventing conversion of condensate, a filter will be carried up aboard Endeavour that should resolve the issue.

"The plan is, as early as we can, to install those new components, before the shuttle arrives, and when the shuttle arrives we'll install the filter and then we'll activate the water processor along with the urine processor and recover our regenerative (environmental control and life support) system by the end of the mission," Suffredini said.

In the meantime, he said the station had plenty of stockpiled water for extended operations while work to fix the current problems is carried out. Depending on how that work goes, some of the life support system racks bound for Tranquility may not be moved into the new module before Endeavour departs.

About the author

Bill Harwood has been covering the U.S. space program full-time since 1984, first as Cape Canaveral bureau chief for United Press International and now as a consultant for CBS News. He has covered more than 125 shuttle missions, every interplanetary flight since Voyager 2's flyby of Neptune, and scores of commercial and military launches. Based at the Kennedy Space Center in Florida, Harwood is a devoted amateur astronomer and co-author of "Comm Check: The Final Flight of Shuttle Columbia." You can follow his frequent status updates at the CBS News Space page.
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